Thank you Jason,
Re the error on the server "Duplicate entry '0' for key 'PRIMARY' "
I found that I had omitted to set the Auto Increment in the boatenquiry table.
I decided to have another go at the insert page and rebuilt this from new. (usefully I found that the Universal Email uses the same recordset as the page to which it is attached).
So, I had it all working very well and then spotted that I had not included the field Sellersemail for inserting.
I rectified that and now it will not insert a record. I cannot see why.
I am attaching that file and wonder if you can see the reason.